title: Growth hormone receptors in testis and liver during the spermatogenetic cycle in rainbow trout (Oncorhynchus mykiss).
abstract: Changes in growth hormone (GH) receptivity in the testis during the reproductive cycle were studied in rainbow trout (Oncorhynchus mykiss). This necessitated setting up a method to characterize GH receptors (GH-R) in crude testis homogenate. Binding of radiolabeled recombinant rainbow trout GH (125I-rtGH) to crude testis preparation was dependent on testicular tissue concentration. The sites were specific to GH, with no affinity for prolactins, gonadotropins, or insulin. Similar high affinities for 125I-rtGH were obtained with crude testis (4.5 x 10(9) + 0.25 M(-1)) and crude liver preparations (5.1 x 10(9) +/- 0.06 M(-1)) at all stages of spermatogenesis, as well as with testicular membrane preparations (2.4 x 10(9) M(-1)). GH-R concentration in testis was high during the immature stage (590 fmol/g testis); it then decreased regularly from the beginning (stage II, spermatogonia proliferation: 706 fmol/g testis) to the end of spermatogenesis (stage VII: 158 fmol/g testis). Conversely, the absolute testicular capacity increased dramatically between stages IV and VI (1.2-16.2 pmol/2 gonads), when testicular growth is extremely rapid. GH-R concentration in the liver was highest in early stages (6.5-6.7 pmol/g liver); this value then significantly decreased during midspermatogenesis (stage VI: 3.5 pmol/g liver) and returned to immature levels at the end of the cycle. No significant correlation was found between GH-R in testis, GH-R in liver, and plasma GH concentration. Preliminary experiments performed on isolated populations of testicular cells revealed that binding of 125I-rtGH was detectable in Sertoli cell-enriched fractions but not in germ cell populations. We conclude that GH-R are present in the testis during the entire reproductive cycle in rainbow trout, probably in somatic cells and in particular in Sertoli cells.
authors.affiliation: Laboratoire de Physiologie des Poissons, INRA, Campus de Beaulieu, Rennes, France.
authors.forename: J M
authors.initials: JM
authors.lastname: Gomez
authors.forename: M
authors.initials: M
authors.lastname: Loir
authors.forename: F
authors.initials: F
authors.lastname: Le Gac
mesh_terms: D000818:Animals; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism*; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000502:physiology*; D011986:Receptors, Somatotropin / Q000378:metabolism*; D013091:Spermatogenesis / Q000502:physiology*; D013737:Testis / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D011986:Receptors, Somatotropin; D013006:Growth Hormone